Ventilating fan



Dec. 12, 1939. H, KR 2,183,079

' VENTILATING FAN Filed Feb. 11, 1938 "ma-"Fora2r" w as w m m yaw A WITNESSES: INVENTOR Z i I Herman/2 fi rofp 7% ATTORNEY trifugal type, which rotate at relatively higlr.

Patented Dec. 12, 1939 vENTrLA'rmG V I Hermann Kropp,Nuremberg, Germany, assignor to Westinghouse Electric '& Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 11, 1938, Serial'No. 189,981

InG

ermany February 12,1937

3 Claims. (01. 230-127) The present invention relates to the construction of ventilating fans "or blowers for the purpose of reducing the noise caused by them, and particularly 'the 'so-called siren tones. It is especially applicable to the fans of dynamo-electric machines, although it is not limited to this particular type of fan.

Ventilating fans, especially those of the censpeeds usually run in housings or other enclosures which have openings for the escape of air discharged from the fan. These openings and the internal ribs or other irregularities in the hous ing cause the air to be discharged; in a discontinuous manner, 1. e'., in afseries of impulses or jets. The effect of this, is to cause considerable noise during operationof the fan'and, in particular, it causes an action similar to that of a siren which gives rise to a high-pitched very objectionable sound.

The object of the present invention is to provideia fan construction which will substantially eliminate, or at least greatly reduce, this objectionable noise.

A more specific object. of the invention is to provide a fan construction which will break up the stream of air discharged from the fan and cause eddies therein so as to prevent the discharge of air in jets.

These objects are attained by providing a circular member, preferably of sheet metal, which has perforations formed in it and which encircles the fan and is secured to the outer ends of the blades. The effect of this perforated member is to break up the stream of air discharged from the fan and to cause eddies in it. This action eliminates the siren efiect and also substantially re duces other noises caused by the,Loperation/of' the fan. Instead of a sheet metal member, any, other suitable perforated element maybe used, such as a wire grid; or even, in some cases, a coarse meshed wire gauze.

The invention will be m'ore fully understood from the following detailed descriptiontaken in (connection with the accompanying drawing, in

which: I v I I Figure l is a longit dinal sectional view of one end of a dynamo-e1 ctric machine having a fan according to the pre ent invention; and

Fig. 2 is a plan view of the fan shown in Fig. 1.

In the drawing, the invention is shown as applied to a fan or blower for a dynamo-electric machine having a stator member, part of which is shown at l, and a rotor member having a suitable shaft 2 which is supported for rotation in a bearing 3. An end bell 4 is secured to the stator member I by screws 5 or other'securing means, and has openings 6 formed in it for the discharge of air.

A fan or blower indicated generally at 1 is mounted on the'shaft 2 to draw air through the machine in order to ventilate it. This fan con sists of a hub portion 8 which is keyed or otherwise secured to the shaft andwhich supports inner and outer shroud rings 9 and I0, respectively, between which are secured a plurality of generally radial blades H. A perforated member l2, which is preferably in the form of a sheet metal cylinder, encircles the outer circumference of the manufacture, is circular, as shown in the drawing. 5

The circumferential spacing of the perforations is less than the spacing of the outer ends of the so arranged th e perforations of adjacent rows should be displaced in a circumferential direction a distanceless than the spacing between perforations in the same row, as clearly shown in. Fig. 2.

In operation, the air drawn through the machine by the blower, 'as shown by the arrows in Fig. 1, is discharged through the perforations of themember 12 but because of the spacing and relatively small" size of these perforations, the stream ff of air is broken 'up and turbulence and eddiesare produced in it. This prevents the discharge of the airin a series of impulses and thus effectively prevents any siren effect with its resultant objectionable noise.

Although the perforated member 12 has been shown as a sheet metal cylinder fitting over the outside of the fan, it will be apparent that other types of such members could be used. In general, any suitable perforated material can be utilized for this purpose, provided the size and spacing of the perforations and the direction of their edges are such as to break up the stream of air in the manner described above.

Although the invention has been described in connection with a ventilating fan for a dynamoelectrlc machine, it will be apparent that it is not limited to such fans but may be applied to any ventilating fan or blower which operates within a housing at relatively high speed, and where it is desirable to eliminate or substantially reduce the noise caused by the fan.

While a specific embodiment of the invention has been illustrated and described, it is to be understood that it is not limited to the particular construction shown, but that, in its broadest aspect, it includes all equivalent embodiments which fall within the scope of the appended claims.

I claim as my invention:

1. A ventilating fan comprising inner and outer shroud rings, a plurality of generally radial blades secured between the rings, and a cylindrical rim member encircling the outer periphery of the fan in contact with the ends of the blades, said rim member having perforations therein spaced closer to each other than the spacing between the outer ends of the blades and being disposed with their edges non-parallel to the outer peripheral edges of the blades, whereby the flow of air discharged from the fan is broken up and made turbulent.

2. A ventilating fan comprising inner and outer shroud rings, a plurality of generally radial blades secured between the rings, and a. cylindrical rim member encircling the outer periphery of the fan in contact with the ends of the blades, said rim member having perforations therein arranged in a plurality of circumferential rows, the perforations of each row being spaced closer to each other than the spacing between the outer ends of the blades, the perforations of adjacent rows being displaced circumferentially, and said perforations being disposed with their edges non-- parallel to the outer peripheral edges of the blades, whereby the flow of air discharged from the fan is broken up and made turbulent.

8. In a dynamo-electric machine, a stator member, an end bell secured to the stator member and having openings therein for the escape of ventilating air, and a fan in the end bell to draw air through the machine, said fan corrprising inner and outer shroud rings, a plurality of generally radial blades secured between the rings, and a cylindrical rim member encircling the outer periphery of the fan in contact with the ends of the blades, said rim member having perforations therein spaced closer together than the spacing between the outer ends of the blades and being disposed so that their edges are non-parallel to the outer peripheral edges of the blades and to the edges of the openings in the end bell.

HERMANN KROPP. 

